The Transgenic Mouse/ES Cell Shared Resource facilitates the generation, maintenance, and storage of genetically modified mice, thereby providing useful animal models for the study of diabetes, obesity, and the mechanisms controlling carbohydrate, fat, and protein homeostasis. This facility has been in operation and supported by the DRTC for over 12 years and currently provides nine different services related to the production and maintenance of genetically modified mice. During its history, the Transgenic Mouse/ES Cell Shared Resource has served 131 different investigators by generating over 1755 transgenic founder mice from 482 distinct DNA constructs and 2566 chimeric mice from 203 different ES cell clones. The Shared Resource has further assisted in the generation of at least 101 different genetically modified mice using homologous recombination in embryonic stem (ES) cells. Many of the genetically modified mice have been used by investigators at Vanderbilt and other institutions to gain insight into the function of pancreatic islets, the liver, skeletal muscle, and fat and to study complications of diabetes such as diabetic nephropathy. Other services provide by this core include assisted reproduction to maintain founder lines that are no longer breeding, embryo and sperm cryopreservation, and Cre and Flpe manipulation of conditional alleles. By working closely with DRTC-affiliated investigators to provide advice and instruction on mutant mouse production, screening strategies, maintenance, and analysis of the animals generated, the facility provides state-of-the-art, cost-effective, quality-controlled, and efficient approaches for the generation of genetically modified mice for DRTC-affiliated investigators. This core is part of the Vanderbilt shared facilities system, which provides an efficient billing system and oversight and governance for the core. This core will continue to provide essential services that support the research of DRTC-affiliated investigators in the next funding cycle.